Clinical trauma severity of indoor and outdoor injurious falls requiring emergency medical service response

Background Injurious falls represent a significant public health burden. Research and policies have primarily focused on falls occurring indoors despite evidence that outdoor falls account for 47–58% of all falls requiring some medical attention. This study described the clinical trauma severity of indoor versus outdoor injurious falls requiring Emergency Medical Services (EMS) response. Methods Using the 2019 National Emergency Medical Services Information System (NEMSIS) dataset, we identified the location of patients injured from falls that required EMS response. We classified injury severity using (1) the Revised Trauma Score for Triage (T-RTS): ≤ 11 indicated the need for transport to a Trauma Center; (2) Glasgow Coma Scale (GCS): ≤ 8 and 9–12 indicated severe and moderate neurologic injury; and (3) patient clinical acuity by EMS: Dead, Critical, Emergent, Low. Results Of 1,854,909 encounters for patients with injurious falls, the vast majority occurred indoors (n = 1,596,860) compared to outdoors (n = 152,994). For patients who fell indoors vs outdoors on streets or sidewalks, the proportions were comparable for moderate or severe GCS scores (3.0% vs 3.9%), T-RTS scores indicating need for transport to a Trauma Center (5.2% vs 5.9%) and EMS acuity rated as Emergent or Critical (27.7% vs 27.1%). Injurious falls were more severe among male patients compared to females and males injured by falling on streets or sidewalks had higher percentages for moderate or severe GCS scores (5.2% vs 1.9%) and T-RTS scores indicating the need for transport to a Trauma Center (7.3% vs 3.9%) compared to falling indoors. Young and middle-aged patients who fell on streets or sidewalks had higher proportions for a T-RTS score indicating the need for Trauma Center care compared to those in this subgroup who fell indoors. Yet older patients injured by falling indoors were more likely to have a T-RTS score indicating the need for transport to a Trauma Center than older patients who fell on streets or sidewalks. Conclusions There was a similar proportion of patients with severe injurious falls that occurred indoors and outdoors on streets or sidewalks. These findings suggest the need to determine outdoor environmental risks for outdoor falls to support location-specific interventions.


Introduction
Falls represent an enormous global public health burden associated with significant disability and mortality, with a worldwide age-standardized incidence of 2238 falls per 100,000 persons per year in 2017, over 16.6 million years of life lost, and an average loss of 4% of one's full health status from one fall (James et al. 2020).The US Centers for Disease Control and Prevention (CDC) reported 7.9 million unintentional injurious falls in 2019, associated with 131.5 billion USD in medical costs (Injury Center CDC 2023).Although falls affect all ages, the burden of falls in the US is disproportionately borne by older persons, for whom falls are the leading cause of disability and functional decline (James et al. 2020; Panel on Prevention of Falls in Older Persons 2011).
Research and policy attention has been primarily devoted to falls occurring indoors (Panel on Prevention of Falls in Older Persons 2011; American Geriatrics Society, British geriatrics society, and American academy of orthopaedic surgeons panel on falls prevention 2001) despite reports that among community-dwelling adults, outdoor falls account for 47-58% of falls requiring at least some medical attention (Li et al. 2006;Timsina et al. 2017).The CDC's Web-Based Injury Statistics Query and Reporting System (WISQARS), the Behavioral Risk Factor Surveillance System (BRFSS) and the National Health Interview Survey (NHIS) are primary public health surveillance systems in the US for fall-related injuries (Injury Center CDC 2023;Timsina et al. 2017;Moreland et al. 2020).However, none of these systems routinely provide data on the locations in which falls occur.To improve the surveillance of outdoor falls, Rundle et al. (2023) developed a methodology to identify injurious falls by indoor versus outdoor location using Emergency Medical Services (EMS) clinical and administrative data from the National Emergency Medical Services Information System (NEMSIS) (Rundle et al. 2023).Among the 1,854,909 injuries from falls that required an EMS response in 2019, 129,408 of these fall injuries were identified as occurring outdoors on streets and sidewalks, a number which is 70% higher than the number of pedestrians reportedly injured by automobiles (Li et al. 2006;Timsina et al. 2017;National Highway Traffic Safety Administration 2019).
While establishing surveillance methods is a critical first step towards developing interventions to reduce outdoor falls, epidemiological data are still needed to understand the public health and clinical burden of outdoor falls.Specifically, improved understanding of the clinical severity for fall injuries is critical to determine the short-and longterm burdens of 1) morbidities and disability among individuals (Stewart Williams et al. 2015) and 2) health care utilization needs of different populations (Eliacin et al. 2021;Korley et al. 2016), particularly in light of potential differences across sociodemographic groups (Chun Fat et al. 2019;Sharma et al. 2018).In the immediate setting following an injury, clinical severity scoring tools have been recommended, including the Revised Trauma Score for Triage (T-RTS) and Glasgow Coma Scale (GCS), to help guide on-scene EMS to determine the severity of the injury and optimal care response for the individual (Champion et al. 1989;Newgard et al. 2022).
There are very few available studies that compare the severity of indoor and outdoor falls, with the focus of these being among the older adult population (Bath and Morgan 1999;Chippendale et al. 2017;Kelsey et al. 2010Kelsey et al. , 2012;;Kim 2016;Lee 2021;O'Loughlin et al. 1994).Chippendale et al. 's (2017) study of older U.S. trauma center patients who sustained outdoor falls had a higher frequency of open wounds and head injuries compared to indoor falls, but no significant difference on the injury severity score (ISS).Kim (2016) found that outdoor falls led to a higher proportion of head and neck injuries than indoor falls among older emergency department patients across 20 hospitals in Korea.Jung et al. 's study (2018) indicated that the likelihood of severe injury, as determined by level of care, from outdoor falls in older adults was higher in men compared to women.Overall, these studies were limited by examining only individuals admitted to a hospital, and none examined a national sample.Furthermore, assessment of outcomes and measures of injury severity varied across these studies limiting the ability to compare findings.
National surveillance data comparing indoor and outdoor injurious falls are almost non-existent, yet critical to the development of person-centered, community-specific programs and policies to prevent serious falls.Data from EMS responses on the clinical trauma severity and level of care for indoor and outdoor injurious falls could be particularly informative from a healthcare resource perspective.Here we use 2019 national U.S. EMS data to describe the clinical trauma severity of indoor versus outdoor injurious falls, and to describe these patterns by patient demographic characteristics.

Study design
This cross-sectional study of EMS records from the 2019 National Emergency Medical Services Information System (NEMSIS) Public-Release Research Dataset included 1,854,909 occurrences of falls requiring EMS response across US states and territories (Rundle et al. 2023).

Data source
NEMSIS is the national system to collect and standardize data from EMS agencies across the US that is administered by the National Highway Traffic Safety Administration (NHSTA) Office for Emergency Medical Services.The NEMSIS data are public, de-identified, and HIPAA exempt data released by the University of Utah, as such further Institutional Review Board (IRB) review was not requested (Dawson 2006;Ehlers et al. 2023).The use of NEMSIS to identify falls and locations of falls have been previously described and includes a robust approach to identifying overall injurious falls and to identifying falls for which syncope (heat-related and non-heat related syncope) and heat illness were contributing factors Rundle et al. (2023).EMS data entry into NEMSIS must abide by the standards set forth by the NHTSA Office of EMS and outlined in the NEMSIS data dictionary (https:// nemsis.org/ media/ nemsis_ v3/ relea se-3.5.0/ DataD ictio nary/ PDFHT ML/ EMSDE MSTATE/ index.html) (NEMSIS 2024).

Study variables and inclusion criteria
Detailed methods for inclusion criteria and coding of fall locations (indoor, outdoor -not on street or sidewalk, outdoor -on street or sidewalk, indoor/outdoor unclear), patient demographic variables, and on-scene clinical measures (e.g.patient acuity) can be found in Rundle et al. (2023).Briefly, we used NEMSIS variables ePatient 13, ePatient 15 and eSituation 13 to define patient sex (male, female) and age groups (0-20, 21-30, 31-40, 41-50, 51-60, 61-65, 66-70, 71-75, 76-80, 81-85, 86-90 and 91 + years).Falls with EMS notations of seizures have been removed from the analyses.NEM-SIS data includes the patient's clinical acuity, rated by EMS, which is classified as: Dead Without Resuscitation Efforts, Critical, Emergent, Low, Unknown.NEMSIS data were also used to calculate the Revised Trauma Score for Triage (T-RTS) and the Glasgow Coma Scale (GCS).The T-RTS, GCS and patient acuity data were used to characterize the severity of the injuries as observed by the EMS clinician on scene.When the tests used to calculate the GCS and the T-RTS were administered multiple times for a patient, the mean of all administrations were used.Sensitivity analyses were repeated using the first, maximum (or best), and minimum (or worst) scores for GCS and T-RTS.

Revised trauma score for triage (T-RTS)
The Revised Trauma score for Triage to a Trauma Center (T-RTS) is a modified version of the original Trauma Score, that is more reliable and excludes capillary refill and respiratory expansion which are more difficult to assess in the field by EMS (Champion et al. 1989).The T-RTS can be used by EMS to make decisions on trauma care based on the severity of patient injuries (Lichtveld et al. 2008).For each patient, we calculated the mean T-RTS by summing the average value for GCS, systolic blood pressure, and respiratory rate.Champion and colleagues evaluated T-RTS cut-points based upon survival probabilities to create decision rules for patients to be triaged to a trauma center (Champion et al. 1989).Decision Rule 2 was used for the present study to categorize the T-RTS score into: ≤ 11, indicated need for immediate transport to a Trauma Center designated hospital; > 11 does not.As blood pressure may be artificially lowered by anti-hypertensive medications, the use of which differs by age group, the validity of the T-RTS may vary by age.Therefore, we decided a priori to also assess GCS alone as a second measure of injury severity that is independent of blood pressure.

Glasgow coma scale (GCS)
The Glasgow Coma Scale (GCS) is a well-established measure of neurological status used for risk stratification in acute neurosurgical or traumatic injuries; the scale ranges from 3 to 15 and is calculated by summing the values for eye opening, verbal response, and motor response for each patient.In contemporary clinical practice, the GCS is used to determine the risks of mortality and morbidity, and more urgently to guide acute clinical management.We calculated the mean Glasgow Coma Scale (GCS) by summing the average value for eye opening, verbal response, and motor response for each patient.GCS ranges from 3 to 15, and for this analysis, we used the common GCS classifications for injury severity: severe, ≤ 8; moderate, 9-12; and minor, ≥ 13 (Jain and Iverson 2024).

Statistical analyses
We conducted descriptive analyses for all EMS encounters for injurious falls by comparing the T-RTS, GCS, and patient acuity classifications by fall location, and further described these analyses by patient demographics.All results were interpreted among non-missing data.Due to the large size of this dataset, we did not include measures of statistical significance as even quite small differences in percentages reported within tables and cross-tables are statistically significant.Instead, we allow the readers to make interpretations based on practical relevance in the differences.We conducted all analyses in R statistical software (v4.3.1;R Core Team 2023).

Results
Table 1 reports on the location of fall injuries by injury severity scores.In total 1,854,909 injuries from falls that required an EMS response were identified in the 2019 NEMSIS data.While the majority of falls occurred indoors (91%), among falls occurring outdoors, 85% occurred on streets and sidewalks.For patients who fell indoors compared to outdoors on streets or sidewalks, proportions were similar for moderate or severe GCS scores, T-RTS scores indicating need for transport to a Trauma Center and EMS acuity rated as Emergent or Critical.Patients injured by falling outdoors not on a street or sidewalk had a lower percentage for moderate or severe GCS scores and for T-RTS scores indicating the need for transport to a Trauma Center compared to percentages for those injured by falling outdoors on streets or sidewalks, but the reverse pattern was observed for patients injured by falls with an Emergent or Critical patient acuity.
Table 2 reports on the location of fall injuries by injury severity scores and by patient sex.A higher proportion of male patients had injuries rated as Critical or Emergent, had moderate to severe GCS scores and had T-RTS scores indicating the need for transport to a Trauma Center, than female patients.The proportions for male patients injured by falls who had moderate or severe GCS scores and T-RTS scores indicating the need for transport to a Trauma Center were also higher for outdoor falls on streets or sidewalks compared to indoor falls.While among female patients, the percentages for moderate or severe GCS scores and T-RTS scores necessitating care at a Trauma Center were more similar for falls on streets or sidewalks and indoors locations.Among male and female patients, the proportions for injurious falls for which patient clinical acuity was rated Critical or Emergent were similar for falls occurring on streets or sidewalks and for falls occurring indoors.
Tables 3, 4 and 5 report on the injury severity measures by the location of fall and by patient age.Young and middle-aged patients (≤ 60 years) who were injured by falls on streets and sidewalks had higher proportions for T-RTS scores indicating the need for transport to a Trauma Center compared to young and middle-aged patients injured by falls occurring indoors.However, older patients (> 60 years) who were injured by falling indoors had higher proportions for T-RTS scores indicating the need for transport to a Trauma Center than older adults who fell on streets or sidewalks.Similar patterns were observed for patients who had moderate or severe GCS scores for falls.Results were essentially the same whether the GCS and T-RTS score were calculated using the mean, or the first, maximum, or minimum scores.

Discussion
The majority of fall injuries to which EMS responded in 2019 occurred indoors, with the second largest category occurring outdoors on streets or sidewalks.However, the proportion of patients who had fall injuries rated as Emergent or Critical, had moderate or severe GCS scores and had a T-RTS score indicating the need for transport to a Trauma Center were similar across indoor and outdoor locations of falls.Given the large numbers of falls that occur indoors and among older persons, it is This study found that the proportion of severe outdoor falls on streets and sidewalks was higher among men   (2017) found that young and middle-age men were more likely to fall outside, whereas older females were more likely to fall inside.Young men were also most likely to fall while engaging in vigorous activity, and thus the potentially higher speed and impact of the activities at the time of falling may result in more serious fall injuries for this subgroup.An additional explanation is that men of all ages tend to consume more alcohol than women, and acute alcohol consumption is associated with greater risk of injurious falls by impacting balance control and cognition (Taylor et al. 2010).One study found that alcohol-related fall injury presentations to emergency departments (ED) were more prevalent among men and younger patients, and were more severe based on triage scale ratings and admissions to the ED compared to nonalcohol-related injuries (Woods et al. 2019).Future work in this area should examine the role of substance use in the severity of injurious falls by location to inform placebased intervention strategies and policies.We also found that outdoor falls on streets or sidewalks had higher proportions for injury severity scores among young and middle-aged individuals compared to indoor falls among this age subgroup, but this pattern was reversed for older adults.This finding may also be explained by the evidence showing a higher proportion of alcohol involved falls among younger adults and greater severity of these falls, which could be occurring on streets or sidewalks near alcohol serving establishments or nightlife districts where alcohol consumption is common (Woods et al. 2019).Indoor falls may be more frequently severe among older adults due to a form of selection bias.Specifically, the population of older adults that fall indoors may be more likely to be frail, while those who fall outdoors may be in better overall health (Kelsey et al. 2012).This is consistent with findings that suggest that outdoor falls are experienced by healthier and more active individuals, compared to the greater risk of falling indoors for individuals in poorer health who may experience worse injury outcomes.(Li et al. 2006;Kelsey et al. 2010).Additionally, older adults often have medical conditions and are more likely to use medications such as psychotropic and cardiovascular drugs that increase their risk of falling (Seppala et al. 2018;Wastesson et al. 2018).Lastly, there may also be differences in the types of surfaces (e.g., wooden floor, grass) or floor characteristics adults are falling on indoors compared to outdoors which could influence injury severity; however, studies are lacking in this area of research (Jung et al. 2018).
Current fall prevention guidelines do not explicitly examine the impact of outdoor environments on falls (Panel on Prevention of Falls in Older Persons 2011; Montero-Odasso et al. 2022) and pedestrian safety policies are largely centered around pedestrian injuries from motor vehicles with minimal attention to outdoor falls, even though these two injury types occur in the same or adjacent physical environments (Evenson et al. 2018).This may be due to the limited empirical evidence available to determine modifiable environmental risk factors 1 GCS, Glasgow Comma Scale  for outdoor falls (Schepers et al. 2017).Li et al. (2006) found that among a sample of U.S. adults, participants subjectively reported that most (73%) of outdoor falls were due to environmental factors such as the condition of the walking surface, and usually occurred on sidewalks, curbs and streets.Yet, rigorous epidemiological studies are still needed to identify potential environmental hazards on sidewalks and streets such as street trees that may cause buckling or damage to sidewalks and increase outdoor fall risk (Bentley 1998;Bentley and Haslam 2001;David and Freedman 1990;Fothergill et al. 1995;Hunt et al. 1991).The described approach using routinely collected EMS administrative and clinical data for surveillance of outdoor injurious falls could be used in future research studies that implement ecological or case-control study designs to identify risk factors for outdoor fall injuries or for evaluating interventions to reduce injurious falls (Mooney et al. 2022).
The primary strength of this study is the use of NEM-SIS data, which provides a well-documented, very large census of health encounters requiring an EMS response.The data include pertinent sociodemographic and clinical information, and variables that can be used to code the location of the encounter, eliminating the need to incorporate additional data sources.While sensitivity analyses revealed that there were essentially no differences in presented findings when using the mean, first, max, or min GCS or T-RTS score, measurement error is still possible given the existing concerns regarding the accuracy and validity of the GCS (Bledsoe et al. 2015).The severity outcome data also had varying degrees of missingness.We were unable to calculate GCS for 7.5% of patients and T-RTS for 13.0% of patients, and 25.9% of patients did not have an acuity measure reported.Also, there are many ICD 10 sub-codes available for defining falls, but it is unclear how much variation there is across  EMS clinicians and companies in coding falls by ICD 10 codes.As such we did not attempt to sub-classify falls by context, such as falls on stairs or falls involving impacts on furniture.This study is also limited by missing data on fall location, but only 6% of fall injuries could not be classified by location.The coding schema used to classify fall location does not make use of narratives and text notes created by EMS personnel, and therefore may result in misclassification of fall location.Machine learning for natural language processing applied to EMS narrative notes could supplement the ICD 10-based case-finding algorithm used in this study and increase the sensitivity of identifying fall location from EMS data (Mayampurath et al. 2021;Zhao et al. 2021).Lastly, the NHIS estimate for the percentage of injurious outdoor falls is substantially higher than we observed in the NEMSIS data (47% vs 9%) (Timsina et al. 2017).NHIS includes injurious falls that required any medical attention and collects data from community dwelling adults, while NEMSIS provides data on EMS responses for all ages and for those living in the community and in nursing facilities.As outdoor falls have been found to occur among those who are younger and healthier (Li et al. 2006;Kelsey et al. 2010), these falls may be less likely to require an EMS response than those occurring indoors and suggests that a selection bias exists within the NEM-SIS sample.As such the differences in the estimates of the proportions of falls occurring outdoors derived from the NHIS and NEMSIS likely reflect differences in the clinical thresholds used for defining an injurious fall and in the populations covered by the two datasets.

Conclusion
In conclusion, these data show that the proportion of severe life-threatening injuries from falls that occur outdoors on streets or sidewalks is similar to that for falls that occur indoors.These findings represent a public concern as the population of persons age 65 years and older is expected to grow by 22% by 2040, and the number of injurious falls and associated healthcare costs will simultaneously increase (Administration for Community Living 2022).Indeed, recent data already shows a rising incidence of falls of 1.5% per year from 2016 to 2019 (Hoffman et al. 2022).These concerns emphasize the need to address outdoor falls in current fall prevention guidelines, and to improve surveillance tools for monitoring outdoor falls and associated risk factors and outcomes.

Table 1
Descriptive statistics for EMS Encounters for Reported Location of Fall Injuries by Patient Acuity, GCS and T-RTS scores. 1 1 GCS, Glasgow Comma Scale; T-RTS, Revised Trauma Score for Triage tion of Falls in Older Persons 2011; American Geriatrics Society, British geriatrics society, and American academy of orthopaedic surgeons panel on falls prevention 2001).However, the comparable trauma severity of outdoor injurious falls compared to those that occur indoors and the greater severity of falls on streets and sidewalks among young and middle-aged patients suggests that additional public health attention is needed to identify modifiable outdoor environmental risk factors to prevent outdoor falls.

Table 2
Descriptive Statistics for EMS Encounters for Reported Location of Fall Injuries by Patient Acuity, GCS and T-RTS Scores, Categorized by Sex. 1

Table 3
Descriptive Statistics for EMS Encounters for Reported Location of Fall Injuries by GCS, Categorized by Age. 1 (Timsina et al. 2017;Kelsey et al. 2012;Duckham et al. 2013)es in age and physical activity status for men and women falling outside versus inside(Timsina et al. 2017;Kelsey et al. 2012;Duckham et al. 2013).Timsina et al.

Table 4
Descriptive Statistics for EMS Encounters for Reported Location of Fall Injuries by Patient Acuity, Categorized by Age

Table 5
Descriptive Statistics for EMS Encounters for Reported Location of Fall Injuries by Need for Triage to a Trauma Center, Categorized by Age. 1